A criminal is brought into a prison for major crimes.

A criminal is brought into a prison for major crimes. The warden informs him that he will be shot in the middle of the prison by 20 of his men. The prisoner is fine with that but he asks for some conditions "All of your men must stand 20 feet away from me and I must be able to select where each of them stands. If I survive, I get to leave."
The warden thinks about it and knows that all of his men will still have an open shot at the criminal, so he agrees.
The next day immediately after the firing squad is positioned the criminal walks out untouched. How did he do it?

He set up all of the warden's men so they are standing directly across from each other. None of them could fire at the criminal because they would risk hitting another man.